Thread-chain cutting device for sewing machines with means for adjusting length of thread remaining on work

ABSTRACT

Thread chain cutting mechanism for sewing machines which includes adjustable means for predetermining the length of thread, chained or not, which is to be left extending from the work after operation of the cutting blades. In one embodiment a fabric guide having a generally horizontally disposed fabric guiding surface is provided with a thread chain inlet opening and is secured for vertical adjustment upon the tube which carries away the cuttings and on which a fixed knife blade is mounted. In another embodiment either or both the tube and the fabric guide is mounted on a frame part of the machine for relative vertical adjustment.

United States Patent 1 n 11 Hume Jurgens 1 1 Judy 31, 11973 [54] THREAD-CHAIN CUTTING DEVICE FOR 3,418,953 12/1968 Fowler 112/252 WING MACHINES WITH MEANS FOR 3,143,987 8/1964 Daniel et al. 112/252 3,541,984 1l/1970 Daniel 112/252 ADJUSTING LENGTH OF THREAD REMAINING ON WORK Inventor: Erwin Jurgens, Hemmingen,

Germany Filed: Apr. 26, 1971 Appl. No.: 137,327

Assignee:

Foreign Application Priority Data May 2, 1970 Germany P 20 21 649.3

US. Cl. 112/252 Int. Cl D05b 65/00 Field of Search 112/252, 130

References Cited UNITED STATES PATENTS 10/1962 Russell et a] 112/252 Primary Examiner-James R. Boler Attorney-James D. Bock ABSTRACT carries away the cuttings and on which a fixed knife blade is mounted. In another embodiment either or both the tube and the fabric guide is mounted on a frame part of the machine for relative vertical adjustment.

1 Claim, 8 Drawing Figures PATENIEU M3 1 SNEETIUFZ FIG! 1 THREAD-CHAIN CUTTING DEVICE FOR SEWING MACHINES WITH MEANS FOR ADJUSTING LENGTH OF THREAD REMAINING ON WORK BACKGROUND OF THE INVENTION In U.S. Pat. No. 2,712,805 a clipper having vertically disposed blades is mounted for vertical adjustment on the machine frame and an air blast tube is provided to direct a thread chain into engagement with the clipper blades while in U.S. Pat. No. 3,149,594 the thread chain is drawn into vertically disposed cutting blades by suction. In U.S. Pat. No. 3,143,987 a fabric guide with inlet opening is mounted to extend in fixed relation with and over both the fixed and movable blades of a pair of horizontally disposed cutting blades. Other horizontally disposed cutting blades or clipper blades are shown in U.S. Pat. Nos. 3,182,620; 3,418,953; 3,554,149; and 3,557,730 with or without suction or air blast means for directing the thread chain to the blades.

The present invention is illustrated in forms in which it is an improvement upon U.S. Pat. No. 3,541,984 which, like many of the patents listed in the preceding paragraph, shows horizontally disposed cutting blades with air blast for directing the thread chain into the blades and in which the fabric is guided over the upper surface of one of the blades whereby variation of length of thread remaining on the work is not possible. While others of the patents listed in the preceding paragraph provide for variation in such length this is not accomplished in a combination in which a fabric guide extends over a pair of cutting blades and in which means is provided for relative adjustment movement between blades and fabric guide.

BRIEF DESCRIPTION OF THE INVENTION The present invention provides a fabric guide which extends over a pair of cutting blades which may be generally similar to or identical with the cutting blades shown in U.S. Pat. No. 3,541,984 aforesaid. Means is provided for changing the spacing between the fabric supporting surface of the fabric guide and the plane in which the cutting blades sever the thread. The fabric guide may be made adjustable relative to the supporting means for the blades or the supporting means for the blades may be made adjustable relative to the fabric guide or both the fabric guide and the supporting means for the blades may be adjustably supported so that either or both may be moved not only to vary the spacing therebetween but also to position the fabric supporting surface of the fabric guide at a desired level relative to other parts of the sewing machine.

For use in a machine in which the fixed cutting blade is attached to a cuttings-receiving tube, as, for example, is shown in said U.S. Pat. No. 3,541,984 the fabric guide, according to the present invention may be directly but adjustably secured to that same tube. Alternatively the tube or the fabric guide, or both, may be so secured to the machine frame as to be adjustable in proper directions to vary the length of the thread, chained or not, left on the work after cutting is completed.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is an isometric view of one fonn of apparatus embodying the present invention, with certain related parts of a sewing machine shown in broken lines;

FIG. 2 is a vertical sectional view taken along the line 2-2 in FIG. 1, with certain additional related parts of a sewing machine shown in broken lines;

FIG. 3 is a plan view of the parts shown in solid lines of FIGS. 1 and 2;

FIG. 4 is a vertical sectional view taken along the line 4-4 in FIG. 3;

FIG. 5 is an isometric view similar to F 1G. I but showing a modified form of apparatus embodying the present invention;

FIG. 6 is a vertical sectional view similar to FIG. 2 but taken along the line 6-6 in FIG. 5;

FIG. 7 is a plan view of the parts shown in solid lines in FIGS. 5 and 6 with a fragmentary showing of a related part of the machine; and

FIG. 8 is a vertical sectional view taken along the line 8-8 in FIG. 7.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Referring first to said U.S. Pat. No. 3,541,984, in which a cutting device of a type to which the present invention may be adapted is shown in somewhat greater delail than is the case herein, it also must be pointed out that the details of the sewing machine to which the present invention may be applied are not shown herein. The present device, for example, may be applied to a wide variety of machines including a machine such as that shown in U.S. Pat. No. 2,704,042 which is referred to in said U.S. Pat. No. 3,541,984 and which is an overedge machine or a combined overedge and chain stitching machine as shown in U.S. Pat. No. 2,973,730.

The apparatus shown in FIGS. ll through 4 comprises a tube 10 into which cuttings are directed, having a fixed notched knife blade 12 secured to the tube 10 and the upper surface of which is flush with the upper surface of tube 10. A movable knife blade i4 is adjustably secured by screw 16 to an arm lb of a lever which is moved by the driving mechanism of the sewing machine (not shown) to reciprocate the movable knife blade 14 in wiping contact with fixed blade 12 to cut thread or thread chain which enters the notch in fixed blade 12. The tube 10 is secured to the machine frame (not shown) by any suitable means such as a bracket 20 which, as shown in FIG. 4, may constitute an extension of tube 20 and may have a horizontally extending portion to which the fixed blade I2 is secured by screws 22.

The tube 10 thus is so positioned in the machine that it extends directly behind the throat plate 24 and presser foot 26 of the sewing machine and the knife blades 12 and 14 are positioned to receive the tails of thread or thread chain which extend from the leading and trailing edges of work pieces successively stitched upon passage through the machine from right to left as viewed in FIG. 2. It will be noted that the upper surface of the fixed knife blade 12 may lie at a level somewhat below the level of the upper surface of the throat plate 24 as shown in FIG. 2 if so desired. An air blast tube 28 is supported on the machine with an outlet so positioned as to direct a blast of air under pressure, in the general direction indicated by an arrow in FIG. 2, thus to direct the thread or thread chain downwardly and rearwardly towards the cutting blades 12 and E4.

The present invention provides a fabric guide which overlies the knife blades 12 and lid and which provides a fabric supporting surface which guides the fabric, comprising the work, above and out of contact with said blades. As shown in FIGS. 1 through 4 the fabric guide 30 consists of a suitably shaped plate having a thread inlet opening 32 of any conventional size or shape. At its forward end the fabric guide 30 turns downwardly and has formed therein a slot 34 elongated in a generally vertical direction to receive a screw 36 threaded into a transversely disposed front wall portion 38 of tube 10. As will be apparent, particularly in FIG. 2, the fabric guide 30 may be secured to tube by tightening screw 36 and the vertical spacing between the upper surface of fabric guide 30 and the plane of the mating surfaces of knife blades 12 and 14 may be varied, within the limits established by the length of the vertically elongated slot 34, simply by selecting a desired vertical position of the fabric guide 30 and tightening the screw 36 in the selected position within slot 34.

Preferably but not essentially, the fabric guide 30 is so shaped as to slope gently downwardly toward the rear that is, toward the left as viewed in FIG. 2. In that event the fabric guide 30 preferably is made of somewhat springy metal or other material which will permit the rear edge of the guide 30 to press upon the upper surface of tube 10 in all positions of vertical adjustment including a lowermost position in which the lower surface of fabric guide 30 rests substantially flat upon the flush upper surfaces of tube 10 and fixed knife blade 12.

In operation of the embodiment of the invention shown in FIGS. 1 through 4 the fabric, comprising successive work pieces being stitched on the sewing machine, leaves the throat plate 24 and is guided over the upper, fabric supporting, surface of fabric guide 30. The remaining tails of thread, chained or not are directed into the thread inlet opening 32 of the fabric guide 30 by the air blast tube 28 whereupon they will be trimmed off to a predetermined uniform length which is dependent upon the position of'vertical adjustment of the fabric guide 30 upon the tube 10. Such predetermined length may be very short, that is of a length corresponding with the combined thicknesses of the fixed knife blade 12 and fabric guide 30 when the latter is in a lowermost position up to a substantially greater length as limited by the length of adjustment slot 34.

It will be recognized that the present invention is not limited to use in combination with an air blast tube such as the tube 28 shown herein. As demonstrated by the US. Patents identified above it is quite customary to utilize suction devices connected with the discharge end ofa tube such as tube 10 shown herein to draw the thread tails into the tube and cutting devices. Such suction means may be used alone or in combination with air blast tubes such as tube 28 shown herein. In any event the cuttings and lint are discharged from tube 10 in the direction of arrow 40 in FIG. 2 for collection and disposition as desired.

The embodiment of the invention shown in FIGS. 5 through 8 comprises a tube 110 with a fixed knife blade 112 secured thereto and a cooperating movable knife blade 114 secured by a screw 116 to a lever 118 all as described above in connection with FIGS. 1 through 5. In this embodiment the fixed knife 112 is secured to a bracket 120 by screws 122 but the bracket 120 is not secured directly to a frame part of the associated sewing machine. Instead, the tube 110 has fixed thereto a downwardly extending spacer bracket 1463 having a vertically elongated adjustment slot formed therein so that the bracket 140 may be adjustably secured to a frame part 121 of the sewing machine (see FIG. il) by means such as screws M4 extending through slot 142 and threaded into the machine part 122. The construction just described enables one to secure the tube and the associated knife blades 1 l2 and 114 to the sewing machine in any position of vertical adjustment as limited by the length of slot 142. For example the tube 110 may be thus secured at will with the knife blades 112 and 114 above, below or level with the upper surface of the throat plate 124 as will be apparent from FIG. 6.

A fabric guide is shown in FIGS. 5 through 8 which is similar in function and purpose to the guide 30 shown in FIGS. 1 through 4. Thus, the fabric guide 130 is provided with a thread inlet 132 of any conventional size or shape to receive thread, chained or not, remaining on the leading or trailing edges of work pieces emerging from the throat plate 124 and presser foot 126 of the sewing machine. The thread is directed into the inlet 132 as by an air blast pipe 128, as shown herein, or alternatively, as discussed above, by suction applied to the discharge end of tube llll or by both air blast and suction as may be desired.

The fabric guide 130 in this modification of the invention is mounted on a frame part of the machine for vertical adjustment independently of and relatively to the tube 110 and associated cutting mechanism. Thus, as shown particularly in FIGS. 6 and 3 the fabric guide 130 has formed thereon or secured thereto a bracket 138, which extends vertically downwardly from the fabric supporting upper surface of the guide 130, and has formed therein an adjustment slot 134 which is elongated vertically. For convenience in assembly the slot 134 is open at the lower end whereby the bracket 138 may be inserted behind the bracket Mil (FIG. 8), the screws 144 being received in slot I34, and both brackets 138 and 140 may be secured in desired positions of vertical adjustment by tightening of the screws 144.

From a consideration of FIGS. 6 and 3 in particular it will be recognized that the fabric guide lS-ZP may be adjusted vertically with respect to the tube lll fl and associated fixed knife blade 112 to vary the length of the thread, chained or not, which is to be left attached to the work. This adjustment may be made irrespective of the particular position of vertical adjustment of the tube 110. Thus, if it is desired to have the upper fabric supporting surface of the fabric guide 3331 generally level with or below the level of throat plate I24 and yet it is desired to leave substantial lengths of thread on the work, the fabric support may be put in desired position and the tube 110 and knife blade 112 ay be lowered to such level as required to accomplish this purpose. Similarly if it is desired to have the fabric supporting surface of fabric guide 130 at or above the level of the throat plate 124 and yet it is desired to leave very short lengths of thread on the work, the fabric guide 130 may be put in desired position and the tube lllll and knife blade 112 may be moved upwardly to such level as required to accomplish this purpose.

Since the fixed knife blade 112 is secured to tube 110 and the movable blade 114 may or may not be so mounted as to move with blade 112 and tube 110 to various positions of vertical adjustment it may be necessary to reset the movable knife blade 114 to proper level to co-operate with blade 112 in any particular position to which the latter may be adjusted. The mechanism for such setting of movable blade 1 14 is not shown herein but is a customary provision in sewing machines to which this invention is adaptable.

Throughout this specification the lengths of thread left extending from a work piece have been referred to as chained or not. Ordinarily such thread lengths are referred to in the art as thread tails or as thread chain" whether or not the threads are actually chained. Therefore, since there are types of stitches which do not form a chain as they extend from one work piece to another and since the present invention isvobviously equally applicable in either case the thread lengths, chained or not, will be referred to in the claims as lengths of thread chain."

I claim:

1. A thread chain severing device for a sewing machine having stitch-forming means including a throat plate, comprising a pair of knife blades having relatively movable cutting edges, pneumatic means for placing a thread chain attached to a work piece between said edges of said knife blades, a fabric guide having a fabric supporting surface extending generally from said stitch-forming means and lying above said pair of knife blades, a tube for guiding cuttings away from said pair of knife blades, one of said pair of knife blades being fixed upon said tube, said fabric supporting surface of said fabric guide being provided with an inlet opening to receive the thread chain and guide it into said tube and between said edges of said pair of knife blades, said tube and said fabric guide each being secured to a frame part of said sewing machine by adjustable means which provide for selection of the level of said cutting edges of said knife blades and of said fabric supporting surface of said fabric guide, respectively, relative to the level of said throat plate of said stitch forming means, and said adjustable means also providing for adjustable fixing of the distance from said fabric supporting surface of said fabric guide to said cutting edges of said knife blades whereby to selectively predetermine the length of thread chain which will remain attached to said work piece after the severing operation of said knife blades.

i I! I i WI 

1. A thread chain severing device for a sewing machine having stitch-forming means including a throat plate, comprising a pair of knife blades having relatively movable cutting edges, pneumatic means for placing a thread chain attached to a work piece between said edges of said knife blades, a fabric guide having a fabric supporting surface extending generally from said stitch-forming means and lying above said pair of knife blades, a tube for guiding cuttings away from said pair of knife blades, one of said pair of knife blades being fixed upon said tube, said fabric supporting surface of said fabric guide being provided with an inlet opening to receive the thread chain and guide it into said tube and between said edges of said pair of knife blades, said tube and said fabric guide each being secured to a frame part of said sewing machine by adjustable means which provide for selection of the level of said cutting edges of said knife blades and of said fabric supporting surface of said fabric guide, respectively, relative to the level of said throat plate of said stitch forming means, and said adjustable means also providing for adjustable fixing of the distance from said fabric supporting surface of said fabric guide to said cutting edges of said knife blades whereby to selectively predetermine the length of thread chain which will remain attached to said work piece after the severing operation of said knife blades. 